With the development of display technology, three-dimensional (3D) stereo display technology has become one of the important technologies used in a display device. Active shutter-type 3D display technology is a 3D display technology that can be implemented at a low cost. Active shutter-type 3D display technology achieves 3D effect by increasing the refresh rate of images and meanwhile by the aid of rapid switch of 3D glasses, thereby allowing a viewer's eyes to watch corresponding left-eye and right-eye images, and thus producing the stereoscopic effect.
Although the active shutter-type 3D display method can display 3D images, there are problems of left-eye and right-eye image crosstalk phenomenon, 3D image blurring and the like due to vision duration effect, which severely affects the 3D viewing effect. In the prior art, the crosstalk phenomenon of 3D images is generally reduced by a method of inserting a black frame, or a method inserting the image of a previous frame (i.e., continuously giving images of two same frames).
The method of inserting a black frame is mainly characterized in that inserting a black picture between display of a left-eye image and display of a right-eye image. That is, during the process of displaying a frame of a 3D image, a display device 01 displays a left-eye image L, a black picture B, a right-eye image R and a black picture B in sequence, as shown in FIG. 1. Meanwhile, in cooperation with the control on a backlight module 02, the backlight module is turned on respectively when the left-eye image and the right-eye image are displayed; the backlight module is turned off when the black pictures are displayed. In addition, with the aid of rapid switch of 3D glasses 03, a left lens is turned on and a right lens is turned off when the left-eye image is displayed, whereas the left lens is turned off and a right lens is turned on when the right-eye image is displayed. Both of the left lens and right lens are turned off when the black pictures are displayed.
The above method can reduce the crosstalk of 3D images to some extent, however since deflection of liquid crystal molecules in the display device needs a certain time for response, the liquid crystal molecules in the upper portion of the display device have already started to rotate when the display device starts to display the black picture after displaying the left-eye and right-eye images, thus causing the picture to get black gradually. Whereas at the same time, since the liquid crystal molecules in the lower portion of the display device have not rotated yet, the picture still remains in the image of the last frame. On the other hand, when the display device starts to display the right(left)-eye image after displaying the black picture, the liquid crystal molecules in the upper portion of the display device have already started to rotate, causing the picture to gradually become the right(left)-eye image. Whereas at the same time, since the liquid crystal molecules in the lower portion of the display device have not rotated yet, the picture still remains in the black picture. This will result in unevenness of the brightness distribution of the whole display device.
Therefore, although the above method of inserting a black frame can reduce crosstalk to certain extent, it will degrade the evenness of brightness of the display device, and thus deteriorate the display quality.
Additionally, the method of inserting the image of the previous frame is mainly characterized in that inserting the image of the previous frame respectively after display of the left-eye image and the display of the right-eye image. That is, during the process of displaying a frame of a 3D image, the display device 01 displays a first frame of left-eye image L1, a second frame of left-eye image L2, a first frame of right-eye image R1, and a second frame of right-eye image R2 in sequence, as shown in FIG. 2. Meanwhile, 3D image display is realized with the aid of rapid switch of the 3D glasses 03 and control on the backlight module 02.
When the above method is used for display, it needs to control the turn-on time of the backlight module. Supposing that the display device scans in a top-to-bottom manner, if the backlight module is turned on at the time of displaying the first frame of left(right)-eye image, the liquid crystal in the upper portion of the display device has completed rotation, the upper portion of the display device displays the first frame of left(right)-eye image. Whereas at the same time, since the rotation of the liquid crystal in the lower portion of the display device is not quick enough, the liquid crystal in the lower portion does not complete rotation yet. Therefore, crosstalk of the image of the last frame will be introduced into the lower portion of the display device. Therefore the crosstalk value of the lower portion of the display device will be large. On the other hand, if the backlight module is turned on at the time of displaying the second frame of left(right)-eye image, when the liquid crystals in the lower portion of the display device have all completely rotated, although crosstalk will not be introduced into the lower portion of the display device (because its image of the last frame is exactly the same as the image of this frame), the upper portion of the display device has started to be filled with the image of the next frame. Therefore the image of the next frame is introduced into the upper portion of the display device, causing the crosstalk value of the upper portion of the display device to be large.
Accordingly, although the evenness of the brightness of the display device is better when the above method of inserting the image of the previous frame is used, the image crosstalk value is still very large.
In conclusion, it is a problem urgently to be solved by a person skilled in the art to ensure both good brightness evenness of the display device and smaller image crosstalk value during display when realizing 3D display.